1983 Volume 47 Issue 7 Pages 568-574
The fractre toughness KIC and limiting strength of TiC-base cermets were determined by means of analysis of the effect of fracture-initiating defect-size on fracture stress. The KIC value of TiC-16-44 mass%Ni alloys increases in the range of 6.0-9.5 MPa\sqrtm with increase in nickel content. The value of KIC (8.2 MPa\sqrtm) of a TiC-28 mass%Ni alloy decreases monotonically to 5.8-6.4 MPa\sqrtm with increase in the content of the added carbides (Mo2C, NbC, TaC, VC) up to 18.5 mol% (added carbides in carbide phase), except for WC addition. The decrease of KIC by adding different carbides is due to the embrittlement of binder phase which is caused by dissolution of titanium and other elements be contained in the added carbides.
By comparing the KIC of TiC-Ni alloys with that of WC-Co alloys, it was found that the KIC for a cermet composed of carbide and metal phases depends mainly on the elastic moduli (E & ν) of the alloy, and also on the critical strain energy release rate (GIC(B.P.)) and volume fraction (f) of metal phase, according to the following equation.
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The limiting strength of TiC-Ni alloys, which is independent of the size of fracture-initiating defect, is raised from 1.98 to 2.57 GPa as the nickel content inceases from 16 to 44 mass%, and is lowered slightly by addition of carbides except tungsten carbide.
